Rear derailleur with a cable guide roller

ABSTRACT

A rear derailleur for a bicycle includes a base member for fixing to a bicycle frame, a movable member for supporting a chain guide, and a linkage mechanism coupling the base member to the movable member so that the movable member is capable of movement relative to the base member. A roller is coupled to the base member for rotation about a rotation axis, wherein the roller includes a cable guiding surface for guiding an inner wire of a control cable. A casing support is provided for supporting an outer casing of the control cable, and a pivot coupling pivotally supports the casing support to the base member so that the casing support pivots around a pivot axis that is spaced apart from the rotation axis.

This application is a division of application Ser. No. 08/774,887, filedDec. 27, 1997 now U.S. Pat. No. 5,904,629.

BACKGROUND OF THE INVENTION

The present invention is directed to bicycle derailleurs and, moreparticularly, to a bicycle rear derailleur having a cable guide rollerfor controlling the orientation of a control cable.

FIG. 1 is a side view of a prior art rear derailleur disclosed in U.S.Pat. No. 4,610,644. As shown in FIG. 1, the derailleur comprises a basemember 2 for rotatably mounting to a fixing member 1 of the bicycle, amovable member 5, and two linkage members 3 and 4 that connect basemember 2 and movable member 5 together so that movable member 5 iscapable of movement relative to base member 2. A chain guide 6 having aguide pulley 61 and a tension pulley 62 is rotatably coupled to movablemember 5 for guiding a chain 17 along a plurality of sprockets of asprocket cluster S. A first spring 13 is disposed between the movablemember 5 and the chain guide 6 for biasing chain guide 6 clockwise, anda second spring 14 is disposed between the base member 2 and the fixingmember 1 for biasing base member 2 clockwise.

The derailleur is operated by a control cable C of the type having aninner wire W that slides within an outer casing O. Outer casing O issupported to base member 2 through a casing support 16, and inner wire Wis connected to movable member 5 through a wire connector 15. Pullinginner wire W causes movable member 5 to move axially toward the largestsprocket S₂ of sprocket cluster S, and releasing inner wire W causesmovable member 5 to move axially toward the smallest sprocket S₁ ofsprocket cluster S. At the same time, the first and second springs 13and 14 balance with each other to adjust the positions of the basemember 2 and movable member 5 to set the radial position of the guidepulley 61 relative to the rear sprocket assembly S. As a result, basemember 2 usually exhibits reciprocating motion in the direction Z.

Since control cable C is rigidly fixed to base member 2, and sincecontrol cable C ordinarily bends approximately 180° before it attachesto the derailleur, control cable C resists the reciprocating motion ofbase member 2 during operation of the derailleur. This can adverselyaffect the proper positioning of the guide pulley 61. Furthermore,movement of base member 2 in the clockwise direction often causes thebend in control cable C to tighten, thus decreasing the efficiency ofthe cable due to increased friction between the inner wire W and theinner surface of the outer casing O.

SUMMARY OF THE INVENTION

The present invention is directed to a rear derailleur having a cableguide roller for controlling the orientation of a control cable andreducing the effect of cable orientation on the operation of thederailleur. In one embodiment of the present invention, a rearderailleur for a bicycle includes a base member for fixing to a bicycleframe, a movable member for supporting a chain guide, and a linkagemechanism coupling the base member to the movable member so that themovable member is capable of movement relative to the base member. Aroller is coupled to the base member for rotation about a rotation axis,wherein the roller includes a cable guiding surface for guiding an innerwire of a control cable. A casing support is provided for supporting anouter casing of the control cable, and a pivot coupling pivotallysupports the casing support to the base member so that the casingsupport pivots around a pivot axis that is spaced apart from therotation axis. More specifically, the pivot axis of the casing supportis positioned in close proximity to an outer peripheral surface of theroller. The pivoting casing support allows the casing to accommodate thereciprocating motion of the base member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a prior art derailleur;

FIG. 2 is a side view of a particular embodiment of a rear derailleuraccording to the present invention;

FIG. 3 is a view taken along line III--III in FIG. 2.

FIGS. 4 and 5 are detailed views showing the operation of the cablecasing support shown in FIG. 2;

FIG. 6 is a detailed view showing the operation of a cable casingsupport that pivots around the rotation axis of the cable guide roller;

FIG. 7 is a side view of an alternative embodiment of a rear derailleuraccording to the present invention;

FIGS. 8A-8B are top and rear views of the guide roller and cable supportcomponents shown in FIG. 7; and

FIGS. 9A-9B are a side view and a rear cross sectional view of the cableguide roller shown in FIG. 7.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 2 is a side view of a particular embodiment of a rear derailleuraccording to the present invention. This derailleur is constructed andoperates substantially the same as the derailleur disclosed in U.S. Pat.No. 4,610,644, except for the features specifically described below.Accordingly, that patent is incorporated herein by reference.

As shown in FIG. 2, the derailleur comprises a base member 2' forrotatably mounting to a fixing member 1 of the bicycle, a movable member5, and two linkage members 3 and 4 that connect base member 2' andmovable member 5 together so that movable member 5 is capable ofmovement relative to base member 2'. A chain guide 6 having a guidepulley 61 and a tension pulley 62 is rotatably coupled to movable member5 for guiding a chain 17 along a plurality of sprockets of a sprocketcluster S. A first spring 13 is disposed between the movable member 5and the chain guide 6 for biasing chain guide 6 clockwise, and a secondspring 14 is disposed between the base member 2' and the fixing member 1for biasing base member 2' clockwise.

The derailleur is operated by a control cable C of the type having aninner wire W that slides within an outer casing O. Outer casing O issupported to base member 2' through a casing support 100, and inner wireW is connected to movable member 5 through a wire connector 15. Pullinginner wire W causes movable member 5 to move axially toward the largestsprocket S₂ of sprocket cluster S, and releasing inner wire W causesmovable member 5 to move axially toward the smallest sprocket S₁ ofsprocket cluster S. At the same time, the first and second springs 13and 14 balance with each other to adjust the positions of the basemember 2' and movable member 5 to set the radial position of the guidepulley 61 relative to the rear sprocket assembly S. As a result, basemember 2' usually exhibits reciprocating motion in the direction Z.

Unlike the derailleur described in FIG. 1, casing support 100 is notimmovably fixed to base member 2'. Instead, casing support 100 comprisesa casing support member 102 (FIG. 3) connected to legs 104 and 108 thatare coupled to a pivot shaft 112 in a parallel relationship to eachother so that casing support 100 pivots around a pivot axis P.Furthermore, inner wire W does not extend directly in a straight linefrom casing support member 102 to wire connector 15. Instead, inner wireW is guided around a surface 116 of a guide roller 120 that is supportedto base member 2' by a shaft 124 (FIG. 2) for rotation about a rotationaxis R. In this embodiment, surface 116 is formed as a groove forentraining inner wire W.

To avoid contamination of roller 120 and inner wire W, base member 2'includes a mounting member for roller 120 and casing support 100 in theform of side surfaces 130 and 134, a bottom surface 138 and a topsurface 142 which form a housing H for substantially enclosing roller120. Legs 104 and 108 of casing support 100 extend along the sidesurfaces 130 and 134, respectively. Top surface 142 defines a slot 150for receiving inner wire W therethrough so that inner wire W mayreciprocate in the direction Y shown in FIG. 2. To keep the exposedportion of inner wire W constant and at a minimum, the top surface 142is formed as a curved surface having a constant radius of curvatureoriginating at pivot shaft P. A stopper 160 is disposed at one end oftop surface 142 to limit the range of motion of cable support 100 andprevent inner wire W from rubbing against the edge of slot 150.

The pivoting construction of casing support 100 allows control cable Cto assume a less curved orientation for reducing the friction betweeninner wire W and outer casing O.

Also, when the derailleur moves axially relative to sprocket cluster Sand base member 2' reciprocates in the direction Z, casing support 100will pivot so as to minimize the resistance to the reciprocating motionof base member 2'.

As shown more specifically in FIGS. 4 and 5, pivot axis P of casingsupport 100 is spaced apart from the rotational axis R of roller 120and, in this embodiment, is positioned in close proximity to or directlyaligns with the outer peripheral surface 154 of roller 120. Thispositional relationship helps ensure that inner wire W exits outercasing in a smooth direction. Indeed, when pivot axis P is aligned atthe outer peripheral surface 154 of roller 120 then inner wire W exitsouter casing O without bending at all, and this positional relationshipwill be maintained throughout the range of motion of casing support 100.

Another very important advantage of locating the pivot axis P of casingsupport 100 away from the rotational axis R of roller 120, andparticularly when the pivot axis P is positioned as described above, maybe understood by referring to FIG. 6. FIG. 6 is a schematic view showingthe orientation of the control cable C if the casing support were topivot around the rotation axis R of the cable guide roller at a constantradius r. The actual casing support is omitted for clarity.

Assume the chain 17 engages one of the sprockets, e.g., sprocket S₁, inthe sprocket cluster S. At this time, springs 13 and 14 balance witheach other to properly position the guide pulley 61 relative to sprocketS₁, and the casing support orients control cable C in position 1. Inthis position, inner wire W extends a distance l(1) from the exitlocation E of control cable C to the contact location A on the cableguide roller. Assume the cyclist maintains the chain around sprocket S₁but decides to switch the chain to a smaller front chainwheel (not shownin the drawings). After the cyclist shifts to the smaller chainwheel,more of the chain 17 needs to be taken up by the derailleur. This isaccomplished by a combination of clockwise movements of base member 2and chain guide 6. As a result of these movements, springs 13 and 14balance with each other so that the casing support orients control cableC in position 2. In this position, inner wire W extends a distance l(2)from the exit location E of control cable C to the contact location B onthe cable guide roller.

Since the inner wire W is tangent to the cable guide roller, l(1)=l(2).However, the length of inner wire W is not constant with respect to afixed point on the cable guide roller. For example, the length of innerwire W from exit location E to the location B in position 1 is (1(1)+thedistance L around the outer periphery of the cable guide roller),whereas the length of inner wire W from exit location E to the locationB in position 2 is only 1(2). Thus, the length L of inner wire W alsomust be taken up as the control cable C moves from position 1 toposition 2. Since the length L will vary depending upon the size of thechainwheels and the selected sprocket in the sprocket cluster S, springs13 and 14 may not always balance properly. In the present invention,however, the pivot axis P of casing support 100 is positioned away fromthe rotational axis R of roller 120. This, in turn, decreases thedistance L to make the balance of the springs 13 and 14 morepredictable. When the pivot axis P of casing support 100 is positionedin close proximity to or directly aligns with the outer peripheralsurface 154 of roller 120, then the length L can be eliminated entirely.This occurs because the exit location E moves away from the cable guideroller as the cable moves from position 1 to position 2 so that1(1)+L=1(2).

FIG. 7 is a side view of an alternative embodiment of a rear derailleuraccording to the present invention. In this embodiment, a cable guideroller 220 is mounted to a base member 2" in an exposed manner. As shownin FIGS. 7, 8A and 8B, a mounting member in the form of a side plate 230is hingedly connected to base member 2" through a hinge pin 232, andanother side plate 234 is connected to hinge plate 230 through aconnecting pin 233 which also rotatably supports guide roller 200. As inthe embodiment shown in FIG. 2, a casing support 200 comprises a casingsupport member 202 connected to legs 204 and 208. Leg 204 is pivotallyattached to side plate 230 through a rivet 244, and leg 208 is pivotallyattached to side plate 234 through a rivet 248 so that casing support200 pivots around a pivot axis P that is paced apart from the rotationalaxis R of roller 220. Also, in this embodiment pivot axis P ispositioned in close proximity to or directly aligns with an outerperipheral surface 254 of roller 220. This embodiment operates in thesame manner as the embodiment shown in FIG. 2.

Since roller 220 is exposed, there is a risk of mud or dirt build up onthe roller. To minimize the effect of such build up, roller 220 isconstructed as shown in FIGS. 9A and 9B. As shown in those Figures,roller 220 comprises an annular base member 250, a plurality of rollerteeth 260 extending radially outwardly from one axial side of basemember 250 (i.e., on the right side in FIG. 9B), and a plurality ofroller teeth 270 extending radially outwardly from the other axial sideof base member 250 (i.e., on the left side in FIG. 9B). As shown in FIG.9A, the plurality of roller teeth 260 alternate with the plurality ofroller teeth 270 when viewed from the side. As shown in FIG. 9B, eachroller tooth 260 includes an inclined upper inner surface 262, a middleside surface 263 having a curved portion 264, and a lower side surface265. Similarly, each roller tooth 270 includes an inclined upper innersurface 272, a middle side surface 273 having a curved portion 274, anda lower side surface 275. The curved portions 264 and 274 are curved tothe shape of inner wire W so that the curved portions 264 and 274alternatingly form an entrainment surface for inner wire W.

When roller 220 is exposed to contamination (mud, water, etc.), innerwire W pushes the contaminant downward toward the lower side surfaces265 and 275. The contaminant then can exit the exposed sides of roller250 so as not to significantly affect the operation of the derailleur.

The hinged construction of side plate 230 allows the roller assembly topivot if the derailleur is subjected to a shock (for example, if thebicycle falls down). However, if desired, roller 220 may be removedentirely by removing hinge pin 232 and discarding the entire rollerassembly. Then the outer casing O of control cable C may be insertedinto a casing support 16' that is attached to or formed as one piecewith base member 2" so that the derailleur operates like the prior artderailleur shown in FIG. 1.

While the above is a description of various embodiments of the presentinvention, further modifications may be employed without departing fromthe spirit and scope of the present invention. For example, the size,shape and orientation of the various components may be changed asdesired for the particular application. See, for example, the differentlocations of wire connector 15 and 15' in FIGS. 2 and 7. If desired,side plate 230 may be formed as one piece with base member 2", and aregular roller may be used in the embodiment shown in FIG. 7 when thederailleur is not intended to be used in harsh environments. A housingsimilar to the housing H in FIG. 3 or other cover may be provided forthe embodiment shown in FIG. 7 for additional protection. The pivotconnection of casing support in both embodiments may be substituted witha casing support member that slides along a surface such as surface 142in FIG. 2. Thus, the scope of the invention should not be limited by thespecific structures disclosed. Instead, the true scope of the inventionshould be determined by the following claims.

What is claimed is:
 1. A cable guide roller for guiding a control cablewire comprising:a base member having a rotational axis; a plurality offirst roller teeth extending radially outwardly from a first axial sideof the base member, wherein each of the plurality of first roller teethforms a radially outermost free end unconnected from any of the otherfirst roller teeth; a plurality of second roller teeth extendingradially outwardly from a second axial side of the base member, whereineach of the plurality of second roller teeth forms a radially outermostfree end unconnected from any of the other second roller teeth; whereinthe plurality of first roller teeth are spaced apart from the pluralityof second roller teeth in a direction of the rotational axis for forminga cable guide therebetween.
 2. The cable guide roller according to claim1 wherein the plurality of first roller teeth alternate with theplurality of second roller teeth when viewed in a direction of therotational axis.
 3. The cable guide roller according to claim 1 whereinthe base member comprises an annular member.
 4. The cable guide rolleraccording to claim 1 wherein a first tooth of the plurality of firstroller teeth includes:an upper inner side first surface; and a middleinner side first surface having a curved portion for entraining thecontrol cable wire.
 5. The cable guide roller according to claim 4wherein the upper inner side first surface is inclined relative to therotational axis.
 6. The cable guide roller according to claim 4 whereinthe first tooth further includes a lower inner side first surface,wherein the middle inner side first surface is disposed between theupper inner side first surface and the lower inner side first surface.7. The cable guide roller according to claim 6 wherein the lower innerside first surface is inclined relative to the rotational axis.
 8. Thecable guide roller according to claim 7 wherein the upper inner sidefirst surface is inclined relative to the rotational axis in a samedirection as the lower inner side first surface.
 9. The cable guideroller according to claim 4 wherein a second tooth of the plurality ofsecond roller teeth includes:an upper inner side second surface; and amiddle inner side second surface having a curved portion for entrainingthe control cable wire.
 10. The cable guide roller according to claim 9wherein the plurality of first roller teeth alternate with the pluralityof second roller teeth when viewed in a direction of the rotationalaxis.
 11. The cable guide roller according to claim 1 wherein each ofthe plurality of first roller teeth includes:an upper inner side firstsurface; and a middle inner side first surface having a curved portionfor entraining the control cable wire.
 12. The cable guide rolleraccording to claim 11 wherein each of the plurality of second rollerteeth includes:an upper inner side second surface; and a middle innerside second surface having a curved portion for entraining the controlcable wire.
 13. The cable guide roller according to claim 12 whereineach upper inner side first surface is inclined relative to therotational axis, and wherein each upper inner side second surface isinclined relative to the rotational axis.
 14. The cable guide rolleraccording to claim 12 wherein each of the plurality of first rollerteeth further includes a lower inner side first surface, wherein themiddle inner side first surface is disposed between the upper inner sidefirst surface and the lower inner side first surface, wherein each ofthe plurality of second roller teeth further includes a lower inner sidesecond surface, and wherein the middle inner side second surface isdisposed between the upper inner side second surface and the lower innerside second surface.
 15. The cable guide roller according to claim 14wherein each lower inner side first surface is inclined relative to therotational axis, and wherein each lower inner side second surface isinclined relative to the rotational axis.
 16. The cable guide rolleraccording to claim 15 wherein each upper inner side first surface isinclined relative to the rotational axis in a same direction as eachlower inner side first surface, and wherein each upper inner side secondsurface is inclined relative to the rotational axis in a same directionas each lower inner side second surface.
 17. The cable guide rolleraccording to claim 16 wherein the plurality of first roller teethalternate with the plurality of second roller teeth when viewed in adirection of the rotational axis.